Methods and apparatus for fabricating a turbine nozzle assembly

ABSTRACT

An apparatus enables a turbine nozzle, including at least two turbine nozzle singlets to be fabricated. Each singlet includes inner and outer bands and a vane extending therebetween. The vane also includes first and second sidewalls coupled together at a leading edge and a trailing edge. The apparatus comprises a fixture, and at least two support members extending from the fixture. Each support member has first and second abutment surfaces, wherein a first of the at least two support members contacts at least one of the leading and trailing edges of a first of the vanes. At least two locating features extend from the fixture, wherein a first of the locating features contacts one of the first and second sidewalls of the first vane. At least two biasing members are coupled to the fixture, wherein a first of the biasing members biases the first vane against the first locating feature.

BACKGROUND OF THE INVENTION

This invention relates generally to gas turbine engines, and moreparticularly, to turbine nozzle assemblies for gas turbine engines.

Known gas turbine engines include combustors which ignite fuel-airmixtures that are channeled through a turbine nozzle assembly towards aturbine. At least some known turbine nozzle assemblies include aplurality of airfoil vanes that are coupled together such that themembers are spaced apart. Within such nozzle assemblies, the airfoilvanes are coupled together by inner and outer band platforms which forma respective radially inner and outer flowpath boundaries. At least someknown outer bands include a forward and an aft hook assembly that areused to couple the turbine nozzle within the engine.

Nozzle assemblies that include a plurality of airfoil vanes aregenerally more durable and experience less flow leakage in comparison toturbine nozzles including only one airfoil vane. Furthermore, suchmulti-vane turbine nozzles are generally cheaper to manufacture andassemble than turbine nozzles having only one airfoil vane. Becauseturbine nozzles may be subjected to high mechanical loads, at least someof such nozzle assemblies are assembled using brazing or weldingoperations. Specifically, the inner and outer band platforms are shapedusing a grinder and are then brazed together to form the turbine nozzleassembly. However, because the grinding process may causeinconsistencies, accurately aligning the turbine nozzle vanes withrespect to the turbine nozzle assembly may be difficult. For example,one member can be slightly angled with respect to the adjacent member,and such misalignment may cause variations in the throat areas betweenadjacent airfoil vanes which could adversely affect engine performance.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a method is provided for fabricating a turbine nozzle.The turbine nozzle includes at least two turbine nozzle singlets, eachturbine nozzle singlet includes an outer band, an inner band, and a vaneextending between the outer and inner bands, and the vane includes afirst sidewall and a second sidewall coupled together at a leading edgeand a trailing edge. The method includes providing a fixture assemblythat includes at least two support members extending from the fixture,at least two locating features extending from the fixture, and at leasttwo biasing members coupled to the fixture. The method further includespositioning each turbine nozzle singlet in the fixture assembly suchthat at least one of each leading edge and each trailing edge is incontact with at least one support member, and such that at least one ofeach first sidewall and each second sidewall is in contact with one ofthe locating features, and securing each turbine nozzle singlet withrespect to the fixture such that at least one biasing member biases eachvane against one of the locating features.

In another aspect, an apparatus is provided for fabricating a turbinenozzle. The turbine nozzle includes at least two turbine nozzlesinglets, each turbine nozzle singlet including an outer band, an innerband, and a vane extending therebetween, and the vane includes a firstsidewall and a second sidewall coupled together at a leading edge and atrailing edge. The apparatus includes a fixture, and at least twosupport members extending from the fixture. Each support member has afirst abutment surface and a second abutment surface, wherein a first ofthe at least two support members contact at least one of the trailingedge and the leading edge of a first of the turbine nozzle vanes. Atleast two locating features extend from the fixture, wherein a first ofthe locating features contacts one of the first sidewall and the secondsidewall of the first turbine nozzle vane. At least two biasing membersare coupled to the fixture, wherein a first of the biasing membersbiases the first turbine nozzle vane against the first locating feature.

In a further aspect, a datum system assembly is provided for use infabricating a turbine nozzle. The turbine nozzle includes at least twoturbine nozzle singlets that each include an outer band, an inner band,and a vane extending therebetween, and the vane includes a firstsidewall and a second sidewall coupled together at a leading edge and atrailing edge. The datum system assembly includes a fixture, at leasttwo rows of support members extending from the fixture, a first of therows of support members for supporting a first of the turbine nozzlevanes, wherein the first row of support members is orientedsubstantially parallel to each other of the rows of support members.Each support member has a first abutment surface and a second abutmentsurface, wherein the first abutment surface and the second abutmentsurface contact at least one of the trailing edge and the leading edge.At least two locating features extend from the fixture, wherein a firstof the locating features contacts one of the first sidewall and thesecond sidewall of the first turbine nozzle vane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary turbine nozzle assemblythat may be used in a gas turbine engine;

FIG. 2 is a perspective view of a fixture assembly used duringfabrication of a turbine nozzle assembly, such as the turbine nozzleassembly shown in FIG. 1

FIG. 3 is a perspective view of the fixture assembly shown in FIG. 2with the turbine nozzle assembly removed;

FIG. 4 is a side view of the turbine nozzle assembly shown in FIG. 1 andinserted into the fixture assembly shown in FIG. 2; and

FIG. 5 is a side perspective view of the turbine nozzle assembly shownin FIG. 1 inserted in the fixture assembly of FIG. 2 during fabrication.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the terms “manufacture” and “manufacturing” may includeany manufacturing process. For example, manufacturing processes mayinclude grinding, finishing, polishing, cutting, machining, inspecting,and/or casting. The above examples are intended as exemplary only, andthus are not intended to limit in any way the definition and/or meaningof the terms “manufacture” and “manufacturing”. In addition, as usedherein the term “component” may include any object to which amanufacturing process is applied. Furthermore, although the invention isdescribed herein in association with a gas turbine engine, and morespecifically for use with a turbine nozzle assembly for a gas turbineengine, it should be understood that the present invention may beapplicable to any component and/or any manufacturing process.Accordingly, practice of the present invention is not limited to themanufacture of turbine nozzle assemblies or other components of gasturbine engines.

FIG. 1 is a perspective view of an exemplary known turbine nozzleassembly 50 that may be used with a gas turbine engine (not shown). Inthe exemplary embodiment, nozzle assembly 50 includes a plurality ofturbine nozzle singlets 90 that are manufactured together to make a onepiece nozzle assembly 50. Each singlet 90 includes an airfoil vane 52coupled together by an arcuate radially inner band or platform 54, andan arcuate radially outer band or platform 56. In the exemplaryembodiment, nozzle assembly 50 is fabricated from three singlets 50.Accordingly, nozzle assembly 50 includes three airfoil vanes 52.However, in an alternative embodiment, nozzle assembly 50 includes twosinglets 90, forming a doublet.

Inner band 54 includes a retention flange 60 that extends radiallyinwardly therefrom. More specifically, flange 60 extends substantiallyperpendicularly from band 54 with respect to a radially outer surface 62of flange 60. Outer band 56 also includes a retention flange 64 thatextends radially outwardly therefrom, and a leading edge hook assembly66 that also extends radially outwardly therefrom. More specifically,outer band retention flange 64 and leading edge hook assembly 66 extendsubstantially perpendicularly from band 56 with respect to a radiallyinner surface 68 of band 56. Surfaces 62 and 68 define a radially outerand radially inner boundary for a flowpath through nozzle assembly 50.

Airfoil vanes 52 are substantially identical and the exemplary nozzleassembly 50 includes a leading airfoil vane 74, a trailing airfoil vane76, and an inner airfoil vane 78. Each airfoil vane 52 includes a firstsidewall 80 and a second sidewall 82. First sidewall 80 is convex anddefines a suction side of each airfoil vane 52, and second sidewall 82is concave and defines a pressure side of each airfoil vane 52.Sidewalls 80 and 82 are joined at a leading edge 84 and at anaxially-spaced trailing edge 86 of each airfoil vane 52. Morespecifically, each airfoil trailing edge 86 is spaced chordwise anddownstream from each respective airfoil leading edge 84. First andsecond sidewalls 80 and 82, respectively, extend longitudinally, orradially outwardly, in span from radially inner band 54 to radiallyouter band 56 and are separated by a distance 87 such that a throat area88 is defined between each airfoil vane 74, 76, and 78.

FIG. 2 is a perspective view of a fixture assembly 92 used to align andretain turbine nozzle singlets 90 during fabrication of nozzle assembly50. FIG. 3 is a perspective view of fixture assembly 92 with turbinenozzle assembly 50 removed. FIG. 4 is an side view of turbine nozzleassembly 50 inserted within fixture assembly 92. FIG. 5 is a sideperspective view of nozzle assembly 50 inserted in fixture assembly 92during fabrication. In the exemplary embodiment, singlets 90 aremanufactured to form turbine nozzle assembly 50. Specifically, singlets90 are brazed to one another to form nozzle assembly 50. In theexemplary embodiment, a leading singlet 94, an inner singlet 96, and atrailing singlet 98 are manufactured together to form nozzle assembly50.

Each singlet 90 includes inner and outer bands 54 and 56, respectively.Each singlet 90 also includes airfoil vane 52 having first sidewall 80,second sidewall 82, leading edge 84 and trailing edge 86. Singlets 90are loaded, or positioned, into fixture assembly 92 prior tomanufacturing.

Fixture assembly 92 includes a fixture 102, a datum system assembly 104,and a plurality of biasing members 106 coupled to fixture 102. Fixtureincludes a platform 108 having a planar top surface 110, a firstextension arm 112 extending from a first end 114 of platform 108, asecond extension arm 116 extending from a second end 118 of platform108, and a beam 120 extending between the first and second arms 112 and116, respectively. In the exemplary embodiment, a first end 122 of beam120 is rotatably coupled to a pin 124 extending through a top end 126 offirst arm 112. A second end 128 of beam 120 is removably coupled to atop end 130 of second arm 116. A removable pin 132 is removably coupledto second arm 116 and beam 120 to facilitate coupling beam 120 to secondarm top end 130. Accordingly, beam 120 can be rotated about first armtop end 126 thereby facilitating providing access for singlets 90 todatum system assembly 104, as described below. Moreover, extension arms116 and 118 each include a fixture pivot bore 134 for attaching fixtureassembly 92 to a pivot member (not shown) such that fixture assembly 92can pivot about a fixture pivot axis 136 during manufacturing of nozzleassembly 50.

In the exemplary embodiment, datum system assembly 104 facilitatessupporting and aligning three singlets 90 for manufacturing.Specifically, datum system assembly 104 facilitates supporting andaligning leading, trailing, and inner airfoil vanes 74, 76, and 78,respectively. Accordingly, datum system assembly 104 includes aplurality of support members 140 and a plurality of locating features142. In the exemplary embodiment, datum system assembly 104 includesthree rows of support members 140 and three locating features 142 whichcorrespond to the three rows of support members 140. In the exemplaryembodiment, datum system assembly 104 facilitates orienting airfoilvanes 74, 76 and 78 such that a substantially uniform throat area 88, asshown in FIG. 1, is formed between each of the vanes 74, 76, and 78 foreach of the turbine nozzle assemblies 50 that are manufactured using thefixture assembly 92. In the exemplary embodiment, a minimum throat area143 is the smallest radius from the trailing edge to the convex side ofthe next airfoil, and fixture assembly 92 facilitates consistentlymanufacturing substantially identical nozzle assemblies 50 by aligningairfoil vanes 74, 76, and 78 prior to manufacturing.

Each support member 140 includes a base 144 extending from planar topsurface 110, a first abutment surface 146 and a second abutment surface148. Base 144 extends a distance 150 from planar top surface 110 suchthat a gap 152 is provided between trailing edge 86 and platform 108when singlet 90 is inserted into datum system assembly 104. First andsecond abutment surfaces 146 and 148, respectively, are oriented suchthat first abutment surface 146 is substantially parallel with planartop surface 110, and second abutment surface 146 extends at an angle αfrom first abutment surface 146. In the exemplary embodiment, angle α isa right angle such that abutment surfaces 146 and 148 form an insertwithin which airfoil vanes 74, 76, or 78 rest. In an alternativeembodiment, angle α is an acute angle such that abutment surfaces 146and 148 have a V-configuration which facilitates retaining airfoil vanes52 between the surfaces 146 and 148. In the exemplary embodiment,support member 140 facilitates supporting airfoil trailing edge 86.Specifically, first abutment surface 146 facilitates supporting firstsidewall 80 adjacent trailing edge 86, and second abutment surface 148facilitates supporting and/or retaining second sidewall 82 adjacenttrailing edge 86. Accordingly, when airfoil vane 52 is properly insertedand positioned in datum system assembly 104, airfoil trailing edge 86 issupported by first abutment surface 146 and is retained by secondabutment surface 148.

In the exemplary embodiment, as shown in FIG. 4, each airfoil vane 52 issupported by an inner support member 156 and an outer support member158. Inner support member 156 is located a distance 160 from inner band54. Outer support member 158 is located a distance 162 from outer band56. The use of a two support member system facilitates providingstability to singlet 90 during the manufacturing process. In analternative embodiment, more or less than two support members 140 areprovided to support each singlet 90.

Locating features 142 include an airfoil locator 170 and a band locator172 for each singlet 90. Each locating feature 142 includes a riser 174extending from planar top surface 110 and a location pad 176 extendingfrom riser 174 to contact singlet 90 when singlet 90 is loaded intodatum system assembly 104. Location pad 176 includes a curved contactingsurface 178 for contacting singlet 90. In an alternative embodiment,contacting surface 178 is flat. In the exemplary embodiment, airfoillocator 170 facilitates locating the corresponding singlet 90 withrespect to the adjacent singlets 90, and airfoil locator 170 alsofacilitates supporting singlet 90 in conjunction with support members140. Specifically, airfoil locator location pad 176 contacts firstsidewall 80 generally equidistantly from leading trailing edges 84 and86, respectively. In an alternative embodiment, location pad 176contacts first sidewall 80 near trailing edge 86. In another alternativeembodiment, location pad 176 contacts first sidewall 84 near leadingedge 84.

In the exemplary embodiment, band locator 172 extends a distance 182from planar top surface 110 to facilitate contacting inner and/or outerbands 54 and/or 56, respectively. Band locator 172 also facilitateslocating the corresponding singlet 90 within fixture assembly 92 withrespect to the adjacent singlets 90. Specifically, band locator 172facilitates aligning inner and outer bands 54 and 56, respectively ofadjacent singlets 90 within fixture assembly 92 so that singlets 90 canbe manufactured. In the exemplary embodiment, band locator 172 contactsouter band 56. Specifically, band locator locating pad 176 contactsouter band radially inner surface 68. In an alternative embodiment,locating pad 176 contacts inner band 54. In a further alternativeembodiment, locating pads 176 are provided for inner band 54 and outerband 56, thereby aligning both bands 54 and 56.

Biasing members 106, shown in FIG. 3, are coupled to fixture 102. Eachbiasing member 106 includes a body 190 extending from fixture 102 and acontacting surface 192 for interfacing with airfoil vane 52. In theexemplary embodiment, biasing members 106 are coupled to beam 120 andare oriented to contact second sidewall 82 adjacent to leading edge 84.Accordingly, biasing member 106 biases airfoil vane 52 against airfoillocator 170. As such, singlets 90 are secured within fixture assembly 92and are positioned relative to one another for manufacturing. In theexemplary embodiment, biasing members 106 are adjustable such that, whensinglets 90 are positioned within datum system assembly 104, biasingmembers 106 can be extended until contacting surfaces 192 interface withairfoil vanes 52. In an alternative embodiment, biasing members 106include a clamp (not shown) that is extendable between a locked and anunlocked position such that when the clamp is in the locked position,contacting surface 192 interfaces with airfoil vane 52.

In the exemplary embodiment, support members 140 and locating features142 are fixedly coupled to platform to facilitate consistently aligningsinglets 90 with respect to fixture 102. Specifically, support members140 and locating features 142 position singlets 94, 96 and 98 withinfixture assembly 92 such that inner band 54 of each singlet 90 issubstantially aligned with respect to each other inner band 54 withinfixture assembly 92, and outer band 56 of each singlet 90 issubstantially aligned with respect to each other outer band 56 withinfixture assembly 92. Moreover, support members 140 and locating features142 are spaced such that a gap 200 having a gap variation width 201, asshown in FIG. 5, is provided between inner bands 54 of adjacent singlets90 and outer bands 56 of adjacent singlets 90. Gap 200 is the braze gaprequired between the singlets 90. The gap variation width 201 is thegrinding process variance in the angle and braze face joint from thegrinding process. Gap variation width 201 is variably selected tofacilitate brazing or welding of singlets 90. In one embodiment, gapwidth 201 is variably selected from a width of approximately 0.001-0.020inches for manufacturing the singlets 90 together. In anotherembodiment, gap width 201 is approximately 0.005 inches formanufacturing the singlets 90 together. By this method gap 200 has noimpact on minimum throat area 143 between trailing edge 86 and firstsidewall 80 such that throat area 88 is substantially uniform betweeneach of the vanes 74, 76, and 78 for each of the turbine nozzleassemblies 50 that are manufactured using the fixture assembly 92.However, in an alternative embodiment, a larger or smaller gap 200 isprovided.

As illustrated in FIG. 5, inner bands 54 of leading, inner and trailingsinglets 94, 96, 98, respectively, are aligned within fixture 102 priorto manufacturing. Specifically, a first gap 202 is shown between leadingand inner singlets 94 and 96, respectively, and a second gap 204 isshown between trailing and inner singlets 98 and 96, respectively.

In the exemplary embodiment, a plurality of wire members 206 extendbetween respective singlets 90. Wire members 206 have a width 208 thatis wider that gap width 200 such that wire members 206 extend beyond gap200. Wire members 208 are coupled to the respective singlets 90 by aprocess such as, for example, a welding process. Accordingly, wiremembers 206 facilitate securing singlets 90 to one another prior tobrazing singlets 90 together to form nozzle assembly 50. In theexemplary embodiment, wire member width 208 ranges from approximately0.025-0.040 inches, wherein 0.030 inches is considered to provide anoptimum width 208 for spanning gap 200 and for welding to singlets 90.In the exemplary embodiment, three wire members 206 are utilized tosecure outer bands 56 of singlets 90 to each other and three wiremembers 206 are utilized to secure inner bands 56 of singlets 90 to eachother. In an alternative embodiment, more or less wire members 206 areutilized to secure singlets 90 to one another. Moreover, a similarprocess of welding wire members 206 between singlets 90 is utilized tosecure outer bands 56 together. Moreover, in the exemplary embodiment,fixture assembly 92 is pivoted about fixture pivot axis 136 to positionthe secured singlets 90 prior to welding wire members 208.

Once singlets 90 are secured to one another, turbine nozzle assembly 50is fabricated by coupling the individual singlets 90 together.Specifically, in the exemplary embodiment, turbine nozzle assembly 50 isfabricated by brazing or welding singlets 90 to one another therebyforming a one piece turbine nozzle assembly 50 having multiple airfoilvanes 52. In the exemplary embodiment, three singlets 90 are fabricatedtogether. In an alternative embodiment, two singlets are fabricatedtogether, forming a doublet.

The above-described turbine nozzle assembly for a gas turbine engine isfabricated in a cost-effective and reliable manner. The turbine nozzleassembly is fabricated from multiple singlets that are oriented within adatum system assembly prior to fabrication. The datum system assemblyfacilitates positioning the singlets in relation to one another foraccurate, precise, and consistent manufacturing of turbine nozzleassemblies. Specifically, the datum system assembly supports the airfoilvane and provides a gap between each of the singlets so that a pluralityof wire members can be welded to the singlets to secure the singlets toone another prior to the singlets being fabricated together by a brazingprocess. Furthermore, because the airfoil vanes are oriented within thedatum system assembly, the turbine nozzle assemblies will bemanufactured such that the throat areas between the airfoil vanes willbe accurately, precisely, and consistently assembled. As a result, theturbine nozzle assemblies facilitate increasing the performance andextending the useful life of the gas turbine engines in a reliable andcost-effective manner.

Exemplary embodiments of fixture assemblies are described above indetail. The assemblies are not limited to the specific embodimentsdescribed herein, but rather, components of each assembly may beutilized independently and separately from other components describedherein. For example, each fixture assembly component can also be used incombination with other fixture assembly components.

While the invention has been described in terms of various specificembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theclaims.

1. A method for fabricating a turbine nozzle assembly wherein the turbine nozzle assembly includes at least two turbine nozzle singlets having an outer band, an inner band, and a vane extending therebetween, each vane includes a first sidewall and a second sidewall coupled together at a leading edge and a trailing edge, said method comprises: providing a fixture assembly that includes at least two support members extending from the fixture, at least two locating features extending from the fixture, and at least two biasing members coupled to the fixture; positioning each turbine nozzle singlet in the fixture assembly such that at least one of each leading edge and each trailing edge is in contact with at least one support member, and such that at least one of each first sidewall and each second sidewall is in contact with one of the locating features; and securing each vane with respect to the fixture, such that at least one biasing member biases each vane against one of the locating features.
 2. A method in accordance with claim 1 wherein positioning each turbine nozzle singlet further comprises aligning the trailing edge of each vane using a first support member and a second support member.
 3. A method in accordance with claim 1 wherein securing each vane further comprises positioning each biasing mechanism against a respective vane.
 4. A method in accordance with claim 1 wherein positioning each vane further comprises positioning the singlets within the fixture assembly such that the inner band of each singlet is substantially aligned with respect to each inner band within the fixture assembly and such that the outer band of each singlet is substantially aligned with respect to each outer band within the fixture assembly.
 5. A method in accordance with claim 4 wherein positioning the singlets within the fixture assembly further comprises positioning the singlets such that a gap is defined between the inner bands of adjacent singlets and between the outer bands of adjacent singlets.
 6. A method in accordance with claim 5 further comprising: positioning at least one wire member across each gap coupling each wire member to the adjacent singlets.
 7. A method in accordance with claim 6 further comprising brazing the singlets together along the length of the gap.
 8. A method in accordance with claim 1 further comprising forming a braze gap within the inner and outer band of each nozzle singlet.
 9. Apparatus for fabricating a turbine nozzle including at least two turbine nozzle singlets, each turbine nozzle singlet including an outer band, an inner band, and a vane extending therebetween, each vane including a first sidewall and a second sidewall coupled together at a leading edge and a trailing edge, said apparatus comprises: a fixture; at least two support members extending from said fixture, each said support member comprising a first abutment surface and a second abutment surface, a first of said at least two support members for contacting at least one of the trailing edge and the leading edge of a first of the turbine nozzle vanes; at least two locating features extending from said fixture, a first of said locating features for contacting one of the first sidewall and the second sidewall of the first turbine nozzle vane; and at least two biasing members coupled to said fixture, a first of said biasing members for biasing the first turbine nozzle vane against said first locating feature.
 10. Apparatus in accordance with claim 9 wherein at least one of said at least two biasing members contacts one of the leading edge and the trailing edge of the first turbine nozzle vane, opposite said first support member.
 11. Apparatus in accordance with claim 9 wherein said at least two support members comprise a first support member and a second support member that are oriented such that the trailing edge of the first vane contacts said first and second support members.
 12. Apparatus in accordance with claim 9 wherein said first abutment surface and said second abutment surface are oriented to enable the trailing edge of at least one vane to be secured therebetween.
 13. Apparatus in accordance with claim 9 wherein said support members and said locating features are configured to substantially align the inner and outer bands of adjacent turbine nozzle singlets within said fixture.
 14. Apparatus in accordance with claim 9 wherein said support members and said locating features are configured to substantially align the inner and outer bands of adjacent turbine nozzle singlets within said fixture such that a gap is defined between the inner bands and the outer bands of adjacent singlets.
 15. Apparatus in accordance with claim 14 wherein at least one wire extends at least partially across each said gap, said wires are configured to fixedly secure adjacent nozzle singlets.
 16. A datum system assembly for use in fabricating a turbine nozzle, wherein the turbine nozzle includes at least two turbine nozzle singlets that each include an outer band, an inner band, and a vane extending therebetween, each vane including a first sidewall and a second sidewall coupled together at a leading edge and a trailing edge, said datum system assembly comprising: a fixture; at least two rows of support members extending from said fixture, a first of said rows of support members for supporting a first of the turbine nozzle vanes, said first row of support members oriented substantially parallel to each other said rows of support members, each said support member comprising a first abutment surface and a second abutment surface, said first abutment surface and said second abutment surface for contacting at least one of the trailing edge and the leading edge; and at least two locating features extending from said fixture, a first of said locating features for contacting one of the first sidewall and the second sidewall of the first turbine nozzle vane.
 17. A datum system assembly in accordance with claim 16 wherein said first abutment surface and said second abutment surface of each support member are oriented to enable the trailing edge of at least one vane to be secured therebetween.
 18. A datum system assembly in accordance with claim 16 wherein said rows of support members and said locating features are configured to substantially align the inner and outer bands of adjacent turbine nozzle singlets within said fixture.
 19. A datum system assembly in accordance with claim 16 wherein said rows of support members and said locating features are configured to substantially align the inner and outer bands of adjacent turbine nozzle singlets within said fixture such that a gap is defined between the inner bands and the outer bands of adjacent singlets.
 20. A datum system assembly in accordance with claim 16 wherein said datum system assembly is configured to align three turbine nozzle singlets for fabrication. 